There has been proposed in the U.S. Pat. No. 4,524,342, a transformer with a toroidal magnetic core, as shown in FIG. 2, in which a plurality of high-voltage unit coils 3A are formed wound around winding frames or bobbins (not shown) respectively, which are arranged in a peripheral direction of the core spaced with each other and the winding end of each unit coil is connected to the beginning end of the adjacent unit coil with an interconnecting wire or the like to form a high-voltage winding 3.
The toroidal magnetic core 1 is formed by a strip material of an amorphous alloy metal, which is wound up so as to have a thickness designated. The core is kept in an insulator case 2.
On the other hand, as shown in FIG. 3, another type of transformer is also proposed prior to the present invention. In this case, the case 2 is comprised of four parts; an inner cylinder 2A and an outer cylinder 2B which are fitted to the inner and outer peripheral surfaces of the core 1, respectively, and an annular top winding frame 2C and an annular bottom winding frame 2D which cover the top and bottom surfaces of the core 1, respectively. This case 2 is provided for covering the core 1 in order to prevent it from distortion and to insulate it electrically against the winding.
On the top winding frame 2C and the bottom winding frame 2D mentioned above, a plurality of grooves 2a are provided radially for fitting the winding conductor therein. The unit coil 3A is wound around, inserted in each groove 2a partially. In this example, the unit coil 3A are electrically connected with each other in series to form a high-voltage winding 3.
Main insulators 4 for insulating a low-voltage winding against the high-voltage winding 3 are arranged so as to cover all the surfaces defined by the high-voltage winding 3 (In FIG. 2, there is shown only the main insulator attached to the top surface of the high-voltage winding 3). The low-voltage winding 5 is wound around the high-voltage winding 3 surrounded with the main insulator. In this example, the low-voltage winding 5 is double-layered. An insulator 6 between the layers insulate one against the other. Each one turn of the low-voltage winding 5, as shown in FIG. 2, is formed with four link-like conductors; the first conductor 5a, the second conductor 5b, the third conductor 5c and the fourth conductor 5d. The former two conductors 5a l and 5b are arranged in the radial direction of the toroidal core 1, along the top surface and the bottom surface of the core, respectively. The latter two conductors 5c and 5d extending in the axial direction of the core along the inside and outside thereof respectively, connect said first two conductors spirally to form one turn of the low-voltage winding.
In both types of transformers mentioned above, each unit coil 3A of the high-voltage winding 3 is formed with a strip-like conductor 3a coiled by the predetermined number of turns so as to be fitted or positioned in the winding bobbin (not shown in FIG. 2) or the winding conductor groove 2a provided on the winding frames 2C and 2D. In the case of FIG. 3, an inter-connecting conductor 3c is extended from the outer end of each unit coil at the outer side of the toroidal core, in order to connect one unit coil with the other adjacent one. Therefore, all the unit coils 3A are electrically connected in series.
In this case, as shown in FIG. 3, the strip-like inter-connecting conductor 3c which is an extension of the unit coil 3A if first folded so as to make right angle with the peripheral direction of the unit coil on the outer side of the unit coil. And this folded part 3b is fixed on the outer side surface of the unit coil 3A with a suitable adhesive tape. Subsequently, this inter-connecting conductor 3c is put over along the outer periphery of the insulating case to the next winding position of the unit coil as the connecting conductor. At this position, the inter-connecting conductor is again folded in the winding direction of the unit coil and the folded part 3d is fixed on the outer surface of the case 2 with a suitable adhesive tape. Then, the strip-like conductor 3a is wound around to form the next unit coil, fixed in the grooves 2a on the winding frames 2C and 2D, which are parts of the case 2.
As mentioned above, in the case that the inter-connecting conductor is formed by folding the outer end of unit coil, it is necessary to fold the strip-like conductor and to fix it by an adhesive tape. However, it takes a long time and is laborious. When the inter-connecting conductor is provided on the outer side of the core, as mentioned above, it is exposed bare. Due to this, the insulating structure of the outer surface of the core becomes very complicated.